1221021205 has 16 divisors (see below), whose sum is σ = 1502215344. Its totient is φ = 952197120.

The previous prime is 1221021203. The next prime is 1221021223. The reversal of 1221021205 is 5021201221.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 77841 + 1220943364 = 279^2 + 34942^2 .

It is not a de Polignac number, because 1221021205 - 2¹ = 1221021203 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221021203) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 412009 + ... + 414961.

It is an arithmetic number, because the mean of its divisors is an integer number (93888459).

Almost surely, 2^1221021205 is an apocalyptic number.

It is an amenable number.

1221021205 is a deficient number, since it is larger than the sum of its proper divisors (281194139).

1221021205 is a wasteful number, since it uses less digits than its factorization.

1221021205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5016.

The product of its (nonzero) digits is 80, while the sum is 16.

The square root of 1221021205 is about 34943.1138423581. The cubic root of 1221021205 is about 1068.8277857729.

Adding to 1221021205 its reverse (5021201221), we get a palindrome (6242222426).

The spelling of 1221021205 in words is "one billion, two hundred twenty-one million, twenty-one thousand, two hundred five".